The Vertical Structure of Spiral Disks

螺旋盘的垂直结构

• 批准号: 1009471
• 负责人: Matthew Bershady
• 金额: $ 69.17万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1009471&HistoricalAwards=false
• 关键词: Vertical; Structure; Spiral; Disks

This project comprises an observational campaign to determine the mass distributions in the disks of large spiral galaxies, and thereby to constrain the importance of dark matter in the inner regions of these systems. The Principal Investigator has, with previous NSF support, led the development of special-purpose integral-field spectrographs (or integral-field units, IFUs) for mapping the motions of stars and gas in galaxies. With this instrumentation, he has recently completed the Diskmass Survey, acquiring multi-color broad-band imaging and integral-field rotation and velocity dispersion maps of galaxy disks oriented face-on to the line of sight. These data suggest that galaxy disks have lower mass-to-light ratios than expected, which implies that there is no large population of faint, very low-mass stars, and that dark-matter halos are dynamically important even in the galaxies' inner regions. However, the conclusions are weakened by uncertainties in the actual thicknesses of the disks along the line of sight. To remedy the situation, the Principal Investigator, his collaborators, and graduate students will conduct further observations, focusing on similar galaxies that are oriented edge-on to the line of sight. Specifically, they will (1) make photometric measurements of 20 galaxies, in strategically chosen wide and narrow infrared spectral bands that will permit the separation of stellar populations of different age; (2) make IFU measurements of the rotation speed and velocity dispersions in edge on disks, as functions of both distance from the galactic center and distance from the disk midplane, and then compare the rates of change of these quantities against dynamical models to constrain the gravitating mass distributions in the disk and the dark halo; and (3) re-examine the Diskmass Survey data to determine if earlier suggestions in one galaxy for systematic variation in stellar motions with age of the population are borne out in the entire sample. The broader impact of this project includes the launching of science programs on NSF-supported instrumentation, graduate student training and mentoring and inclusion of research results in undergraduate course development, and public presentations that disseminate results to a wide audience.

该项目包括一项观测活动，以确定大型螺旋星系盘中的质量分布，从而限制暗物质在这些系统内部区域的重要性。首席研究员在之前美国国家科学基金会的支持下，领导开发了特殊用途的积分场光谱仪(或积分场单元，IFU)，用于绘制星系中恒星和气体的运动图。利用这台仪器，他最近完成了盘团调查，获得了多色宽带成像以及面向视线的星系盘积分场旋转和速度弥散图。这些数据表明，星系盘的质光比低于预期，这意味着没有大量微弱的、极低质量的恒星，即使在星系的内部区域，暗物质晕在动力学上也是重要的。然而，视线方向圆盘实际厚度的不确定性削弱了这些结论。为了纠正这种情况，首席研究员、他的合作者和研究生将进行进一步的观测，重点放在类似的星系上，这些星系指向视线的边缘。具体地说，他们将(1)在战略上选择的宽和窄红外光谱带上对20个星系进行光度测量，以允许分离不同年龄的恒星群；(2)以IFU测量盘边缘的自转速度和速度色散，作为距离星系中心和盘中面距离的函数，然后将这些量的变化率与动力学模型进行比较，以限制盘和暗晕中的引力质量分布；以及(3)重新检查盘状质量调查数据，以确定一个星系中早期关于恒星运动随人口年龄系统变化的建议是否在整个样本中得到证实。该项目的更广泛影响包括启动关于NSF支持的仪器的科学计划、研究生培训和指导以及将研究成果纳入本科课程发展，以及向广泛受众传播结果的公开演讲。